The types for BSON are pretty hard to parse, especially for newbies - a type called M doesn't make clear that it's actually a map without reading the docs first.

I've created at PR: https://github.com/mongodb/mongo-go-driver/pull/143 that adds these aliases - ie bson.Map for what is currently bson.M, and updates the bson documentation to reflect these changes, preferring the fullword aliases over the single letter ones, but acknowledging the single letter ones as  well.